During the past three years this project has developed methods to derive chiasma maps from meiotic observations, gene maps from lod scores, and physical maps from somatic cells, and to integrate all these data efficiently into a chromosome map which gives the correspondence between physical location and genetic map distance. All published data up to the present time and much unpublished data on more than 2331 pairs of loci have been processed for analysis by computer programs that have been thoroughly checked out. These accumulated data, together with the physical and genetic locations of loci obtained by the LRO (likely region of overlap) method are about to be published. Using this information a maximum likelihood linkage map of chromosome 1 has been constructed. In the fourth year we propose to construct maximum likelihood linkage maps for every chromosome in man, test all unassigned loci for linkage to these groups, test hypotheses about interference, sex differences, chiasma distributions, and recombinational variability, and publish the analyses, as a secure base for formal genetics and genetic counseling.